Premium Quality Replacement Part. Spindle Assembly Maintenance-Free Aluminum. 988173 – Gravely Pro-Walk 52 Walk-Behind Mower, Kawasaki FS (SN: 000101 & Above). 988186 – Gravely Pro-Walk 52 Walk-Behind Mower, Kawasaki FS (SN: 000101 – 000399). 988186 – Gravely Pro-Walk 52 Walk-Behind Mower, Kawasaki FS (SN: 000400 & Above). 991080 (Pro-Turn 152) – Gravely Pro-Turn 52 Zero-Turn Mower, Kawasaki (SN: 021000 – 029999). 991080 (Pro-Turn 152) – Gravely Pro-Turn 52 Zero-Turn Mower, Kawasaki (SN: 040000 – 040999). 991080 (Pro-Turn 152) – Gravely Pro-Turn 52 Zero-Turn Mower, Kawasaki (SN: 041000 & Above). 991083 (ZT 52 HD) – Gravely 52 Zero-Turn Mower, Kawasaki (SN: 020000 – 029999). MANUFACTURED TO MEET OR EXCEED OEM PERFORMANCE.